Towards a Better Understanding of Social Responsiveness and Face Processing in Infancy: Eye-Tracking-Based Research Paradigms

Perceiving human faces and responding to them are two key developmental processes enabling infants to connect with the social world in the prelinguistic period. However, research methodologies investigating these skills have some methodological limitations. In particular, social stimuli employed in the eye-tracking lab setting remain insufficient to fully resemble real humans that infants encounter in real life. More importantly, this may create some concerns regarding ecological validity of obtained findings. Therefore, the main aim of this thesis is to overcome these limitations by designing more realistic lab-based research settings. Based on this, empirical studies conducted in Chapters 6 and 7 introduce the newly improved gaze-contingency paradigms. Chapter 6 investigates the predictive value of reduced social responsiveness observed during the gaze-contingent eye-tracking paradigm in infancy for later developmental problems. Chapter 7 extends this paradigm and introduces the gaze-contingent speech paradigm. This empirical study aims to explore whether infants can discriminate between human and human-like inanimate objects in terms of visual attention orientation, face scanning patterns and social responsiveness during the gaze-contingent speech paradigm. The final empirical study aims to overcome methodological problems observed in infant emotional face processing. Accordingly, the main limitation in the research on infants' emotional face processing is to present emotional facial stimuli with broad affective valences (e.g., positive and negative emotions) to infants simultaneously and expect them to compare emotional faces within opposite emotional valences. Therefore, the final empirical study aims to overcome this limitation and test infants' ability to match happy and sad emotions when presented with not opposite affective valence or the same affective valence stimuli respectively. Findings demonstrate that infants' social responsiveness and perceiving faces can be reliably and accurately measured within structured and realistic eye-tracking-based research paradigms. Finally, the contributions of these methodological improvements to infant development research are further discussed.